In a wireless communication network based on LTE (Long_Term_Evolution), a base station (eNodeB) controls communication resources regarding the communication network.
When information is transmitted from a base station to a terminal (i.e. in “downstream communication”), the base station allocates communication resources that transmit information to the terminal to the downstream communication in accordance with reception of the information from an apparatus such as a Serving_Gateway (S-GW) and a Mobility_Management_Entity (MME). In this case, the base station immediately allocates the communication resources to the downstream communication. Therefore, in the downstream communication, a communication delay hardly occurs.
Next, processing in which information is transmitted from a terminal to a base station (i.e. in “upstream communication”) will be described with reference to FIG. 22. FIG. 22 is a sequence diagram illustrating processing in which information is transmitted from a terminal to a base station.
In the upstream communication, the terminal waits for the base station's allocation of second communication resources that transmits a control message (e.g. PUCCH, Physical_Uplink_Control_Channel, hereinafter, expressed as a “first message”) requesting first communication resources that transmit information (first information in FIG. 22) to the base station. The base station allocates the second communication resources regarding the first message to the terminal at a second timing. An interval of the second timing is substantially constant in many cases.
The terminal transmits the first message to the base station using the second communication resources in accordance with allocation of the second communication resources by the base station.
The base station receives the first message and allocates first communication resources to the upstream communication in accordance with the received first message. Thereafter, the base station transmits a control message (e.g. PDCCH, Physical_Downlink_Control_Channel, hereinafter, expressed as a “second message”) regarding the first communication resources to the terminal.
The terminal transmits information using the first communication resources in accordance with reception of the second message.
As described above, it is difficult for the terminal to transmit information in a period until the second communication resources are managed. Therefore, in the communication network, a communication delay occurs.
The base station continuously allocates, to the terminal, communication resources that continuously transmit information in a certain period after the terminal starts transmitting information. In this case, since the communication resources have been allocated to the terminal, the terminal does not need to newly be allocated a communication resource. Therefore, it is possible to transmit information (second information in FIG. 22) without a communication delay.
PTL 1 to PTL 3 disclose techniques for reducing a communication delay.
PTL 1 discloses a service control apparatus having a real time property. First, the service control apparatus receives a message for previously announcing that an application program or the like transmits information to a terminal. Then, the service control apparatus transmits dummy information for managing a communication path that transmits the information in a period from reception of the message to transmission of the information to the terminal by the application program or the like. As a result, a base station manages a communication path that transmits the information in accordance with transmission of the dummy information by the service control apparatus.
The base station manages the communication path in accordance with the dummy information, and therefore, it is possible for the application program or the like to transmit the information without newly managing a communication path. As a result, when the information is transmitted, a communication delay caused by managing a communication path is small.
PTL 2 discloses a band securing apparatus capable of avoiding congestion caused when information is transmitted via a communication network. The band securing apparatus transmits dummy information to a first apparatus in a period (hereinafter, expressed as a “preparation period”) from detection of a request for transmitting data by the first apparatus to transmission of the data by the first apparatus, in the same manner as the service control apparatus disclosed by PTL 1.
PTL 3 discloses a stream distribution apparatus that estimates a congestion state in a communication network. The stream distribution apparatus estimates a magnitude of a transmission rate and a magnitude of a throughput in a communication network on the basis of a period required from transmission of a probe packet to reception of the probe packet.